DISSOCIATION OF BETA-2-MICROGLOBULIN IS RESPONSIBLE FOR SELECTIVE REDUCTION OF HLA CLASS-I ANTIGENICITY FOLLOWING ACID TREATMENT OF CELLS

Beta2-Microglobulin (beta2m) dissociated from surface HLA class I complex following exposure of cells to low pH and was detected in supernatant by radioimmunoprecipitation with specific monoclonal antibodies (mAbs). As the concn of beta2m in supernatant increased, the binding of mAbs, specific for HLA class I heavy chains associated with beta2m, to the cell surface declined. Binding of mAb specific for free HLA class I heavy chain to the cell surface increased after acid treatment. Reassociation with exogenous beta2m confirmed increase in the number of free HLA class I heavy chains on surface of the cells after their exposure to low pH and also at least partially restored the reactivity with mAbs specific to HLA class I heavy chains associated with beta2m. Dissociation of beta2m from CD1 complex following acid treatment was also accompanied with the changes in antigenicity of cell surface CD1 molecules.